Technological Field
The present invention relates generally to an image forming system.
Description of the Related Art
Conventionally, after forming an image on a sheet by an image forming apparatus, the sheet may be processed by a finisher to perform post-printing processes. However, since sheets conveyed to a finisher may sometimes be stuck to each other due to static electricity, the quality of post-printing processes may be degraded.
When conveying a sheet, the static electricity of the sheet is generated by peeling charge when the sheet is peeled off from a roller nip, friction charge due to microslippage of the sheet at the roller nip, charge transfer from the sheet to a guide member, or the like. Such peeling charge, friction charge, charge transfer or the like is easily influenced by a temperature and a humidity environment on sheet conveying routes, the paper quality of a sheet, the toner amount attached to a sheet, the charged quantity of a guide member or the like. Also, the greater the potential difference between the front and back sides of a charged sheet increases, the greater the attractive force exerted between sheets increases. Accordingly, if a post-printing process is performed with sheets stuck together by the attractive force exerted therebetween, the quality of the post-printing process may be degraded. For example, when performing a sheet aligning process for aligning leading or tailing edges of sheets, or when a side edges aligning process for aligning sheets during stacking discharged sheets, if there is generated an inter-paper attractive force which hinders sheets from being aligned due to static electricity, a paper jam or paper damage may occur. It is thereby desirable to eliminate the static electricity of a sheet for preventing the quality of a post-printing process from being degraded.
Because of this, in various conventional techniques, it has been proposed to form a discharging circuit for eliminating static electricity when a sheet comes in contact with a discharging member to conduct static electricity to ground so that the static electricity is eliminated from the sheet (for example, refer to Japanese Granted Patent Publication No. 3478815, Japanese Patent Granted Publication No. 3584145, and Japanese Patent Granted Publication No. 3528047).
Meanwhile, in various conventional techniques, it has been proposed to feed back the reading result of an image formed on a sheet and correct color tones of the image and the like (for example, refer to Japanese Granted Patent Publication No. 5482820 and Japanese Granted Patent Publication No. 5279441).
For example, an image reading apparatus may be provided between an image forming apparatus and a finisher for the purpose of feeding back the reading result of an image formed on a sheet and correcting color tones of the image and the like. In such an arrangement, a paper path through the image reading apparatus is narrower than that in the arrangement in which no image reading apparatus is provided. A sheet is thereby likely to come in contact with the paper path in the image reading apparatus. Accordingly, further static electricity can be generated due to the friction between a sheet and the paper path in the image reading apparatus. In the case where an image reading apparatus is provided between an image forming apparatus and a finisher, thereby, it is impossible to sufficiently eliminate static electricity by the prior art techniques such as described in Japanese Patent Publication No. 3478815, Japanese Granted Patent Publication No. 3584145, Japanese Granted Patent Publication No. 3528047, Japanese Granted Patent Publication No. 5482820 and Japanese Granted Patent Publication No. 5279441.